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Date: Mon, 16 Jul 2018 14:14:09 -0700 (PDT)
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Subject: Re: Simple hash or pseudo-random function
From: gautier_niouzes@hotmail.com
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Xref: reader02.eternal-september.org comp.lang.ada:53852
Date: 2018-07-16T14:14:09-07:00
List-Id: <comp.lang.ada>

Le lundi 16 juillet 2018 19:17:49 UTC+2, Jeffrey R. Carter a =C3=A9crit=C2=
=A0:

> Not sure what you mean by "an integer in a range of minimum length 365". =
You=20
> could simply use a RNG to generate 64-bit values and xor them with your v=
alues=20
> if you want a 64-bit result. By setting the initial seed, the sequence wo=
uld be=20
> repeatable. Ada.Numerics.Discrete_Random would probably serve. If it's to=
o slow,=20
> the PragmAda Reusable Components includes KISS, a very fast, pretty good =
RNG. It=20
> produces 32-bit values, so you'd probably need to call it twice.

The 64-bit value is the *input* and the output is a function of that input =
only.
e.g.
10562032 gives always 211
31375393 gives always 31
85232830 gives always 172
NB: the input codes can appear in a different order, so a pseudo-random *se=
quence* cannot be used.

I've tested different RNG's by initializing them with the input code and us=
ing only the first pseudo-random value using that seed. The good news is th=
at they seem uniformly distributed even with successive seed values, but th=
ey are not random enough when seeds are similar. I'll check Marius' solutio=
n, or a hash function like CRC.